Chapter XXI: Introduction

255. Coloured materials, such as Prussian blue, chrome-yellow, vermilion, &c., are infinitely divided, so to speak, either when ground pure, or mixed with a white material, in a gummy or oily liquid.

The reproduction of the images of coloured objects with these pigments is called the _Art of Painting_.

256. There are two systems of Painting—the one consists in representing as accurately as possible upon a flat surface an object in relief in such a way that the image makes an impression upon the eye of the spectator similar to that which the object itself would produce. This is termed the _Art of Chiaro-’scuro_.

257. There is a means of imitating coloured objects much simpler in its facility of execution than the preceding. It consists in tracing the outline of the different parts of the model, and in colouring them uniformly with their peculiar colours. There is no relief, no projection; it is the plane image of the object, since all the parts receive a uniform tint: this system of imitating is _Painting in Flat Tints_.

PAINTING ON THE SYSTEM OF CHIARO-’SCURO.

258. Are the modifications perceived in a single coloured object, for example, in a blue or red stuff, &c., indeterminable, when these draperies are seen as draperies of a vestment or furniture, with more or less distinct folds, or are they determinable, in given circumstances? This is a question of which I am about to attempt a solution.

259. Firstly, let us distinguish three circumstances in which modifications of colours may be observed:—

1. Modifications produced by coloured lights falling upon the model.

2. Modifications produced by two different lights—as, for example, the light of the sun and diffused daylight—each illuminating different parts of the same object.

3. Modifications produced by diffused daylight.

260. We will suppose that in the two first cases the lighted surfaces are plane, and that all their superficial parts are homogeneous, and in the same conditions, except that of light. In the third case, we shall consider the position of the spectator viewing an object lighted by diffused daylight, the surface of which is not so disposed as to act equally in all its parts upon the light which it reflects to the eye of the spectator.

261. Modifications produced by coloured lights.

Red rays falling on Black make it appear Purple-black.
” White ” Red.
” Red ” Redder.
” Orange ” Redder.
” Yellow ” Orange.
” Deep Green ” Red-black.
” Light Green ” Reddish-grey.
” Light Blue ” Violet.
” Violet ” Purple.

262. Modifications produced by Orange light.

Orange rays falling on—
Black make it appear Maroon, or Carmelite-brown.
White ” Orange.
Orange ” More vivid.
Red ” Scarlet.
Yellow ” Yellow-orange.
Light Green ” Yellow-green.
Deep Green ” Rusty-green.
Light Blue ” Orange-grey.
Deep Blue ” Grey, slightly Orange-grey.
Indigo Blue ” Orange-maroon.
Violet ” Red-maroon.

263. Modifications produced by Yellow light.

Yellow rays falling on—
Black make it appear Yellow-olive.
White ” Light Yellow.
Yellow ” Orange-yellow.
Red ” Orange.
Orange ” Yellower.
Green ” Greenish-yellow.
Light Blue ” Yellow-green.
Deep Blue ” Green-slate.
Indigo ” Orange-yellow.
Violet ” Yellow-maroon.

264. Modifications produced by Green light.

Green rays falling on—
Black make it appear Greenish-brown.
White ” Green.
Green ” More intense and brilliant.
Red ” Brown.
Orange ” Faint Yellow, a little Green.
Green ” Greener, according to its depth.
Indigo ” Dull Green.
Violet ” Bluish-green Brown.

265. Modifications produced by Blue light.

Blue rays falling on Black make it appear Blue-black.
Black ” White ” Blue.
” ” Blue ” More vivid.
” ” Red ” Violet.
{ Brown, having a
” ” Orange ” { pale tint of Violet.
Blue ” Yellow ” Green.
” ” Green ” Blue-green.
” ” Indigo ” Dark-blue Indigo.
” ” Violet ” Dark-blue Violet.

266. Modifications produced by Violet light.

{Very faint
Violet rays falling on Black make it appear {Violet-black.
” ” White ” Violet.
” ” Violet ” Deeper Violet.
{Red-violet
” ” Red ” {Purple.
” ” Orange ” Light Red.
{Brown, with a
” ” Yellow ” {very slight tint
{of Red.
” ” Green ” Light Purple.
{Fine Blue
” ” Blue ” {Violet.
{Deep Blue
” ” Indigo ” {Violet.

267. It is understood that to represent the preceding phenomena exactly, we must take into account the facility with which coloured light penetrates every kind of glass, the more or less intense colour of the stuff, and the kind of scale to which the coloured stuff and that of the transmitted coloured light respectively belong.

268. These observations were made by partially exposing coloured stuffs to the sun’s rays transmitted through coloured glasses. The portion of stuff not exposed to these rays, was lighted by the direct light of the sun. The portion of stuff which received the action of the coloured rays being exposed to diffused daylight, reflected also rays of that light which it would have reflected in case it had been protected from the influence of the rays transmitted to it through coloured glasses.

269. II. Modifications produced by two lights of different intensity.

270. 1. The modification by the light of the sun falling upon one part of the surface of a coloured body, while the other part is enlightened by diffused daylight.

2. The modification produced when two parts of the same object are unequally illuminated by diffused daylight.

_An object lighted partly by the sun, and partly by diffused daylight._

271. To observe this kind of modification properly, let us expose to the sun a square piece of stuff A B, two and a half inches broad (Plate I., fig 4) and place in the middle a piece of black wire _f, fʹ_; then put parallel to this, and in the middle between A and B, two wires _e, eʹ_ and _g, gʹ_, of about three-tenths of an inch in width. The extremity _gʹ_ is fixed upon a perpendicular plane, so high, that all the part B _f, fʹ_ may be in shadow.

272. 1. _If the stuff is red_, the lighted portion A is more orange or less blue than the part B, which is in shade; and the portion _a_ is more orange than the portion _aʹ_, as the portion _b_ is bluer than the portion _bʹ_.

273. 2. _If the stuff is orange_, A is more orange or less grey than B; and the portion _a_ is deeper, more vivid than _aʹ_, as _b_ is more grey and duller than _bʹ_.

274. 3. _If the stuff is yellow_, A is more vivid, more orange than B; _a_ is more so than _aʹ_, as _b_ is duller than _bʹ_.

275. 4. _If the stuff is green_, A is less blue or more yellow than B; and _a_ is of a yellower green than _aʹ_, as _b_ is bluer than _bʹ_.

276. 5. _If the stuff is blue_, A is less violet and more green than B; and _a_ is greener than _aʹ_, as _b_ is more violet or less green than _bʹ_.

277. 6. _If the stuff is indigo_, A is redder or less blue than B; and _a_ is redder than _aʹ_, as _b_ is deeper or bluer than _bʹ_.

278. 7. If the stuff is violet, A is less blue than B; and _a_ is redder than _aʹ_ as _b_ is bluer than _bʹ_.

279. 2nd. Two contiguous parts of the same object unequally illuminated by the same light, when viewed simultaneously, differ from each other, not only in depth of tone, but also in optical composition of colour.

Place half-a-sheet of coloured paper (Plate I., fig. 5) upon the partition _b_, of a chamber receiving diffused daylight by a window _f_: place another half-sheet upon the partition _a_, in such a manner that it will be lighted directly by the diffused light, while the other is only indirectly lighted by reflection from the walls, floor, and ceiling: the diffused light thus reflected being only white light, then stand at _c_, so as to see both half-sheets at once. I shall designate that which is upon the partition _a_, and most lighted, by A, and the other, which is upon the partition _b_, and less lighted, by B.

These letters in the plate indicate the respective positions of the half-sheets.

280. The inference from these observations is, that the colour of the same body varies, not only in intensity of tone, but also of hue, according as it is lighted directly by the sun, by diffused daylight, or by diffused reflected light. This result must never be overlooked whenever we define the colours of material objects.

3rd. _Modifications produced by diffused daylight reflected by a surface all the parts of which are not in the same position relatively to the eye of the spectator._

281. Distant bodies are rendered perceptible to the eye only in proportion as they radiate or reflect, or transmit the light which acts upon the retina.

According to the laws of reflection, it happens that those portions of a surface which are in relief, or hollow, must reflect the light in such a manner, that the eye of the spectator, in a given position, will see these parts very variously lighted, in respect to the intensity of reflected light, so that the parts of this surface will be, relatively to the eye, in the same condition as the homogeneous parts of a plane surface, which are illuminated by lights of unequal intensity.

There will be this difference, however, that the parts of the surface of a body which appears to us hollow, and especially in relief, being but feebly varied in the greater number of contiguous parts, there will be generally a gradual diminution of the effects observed in the case in which we have studied the modifications of two plane homogeneous surfaces, lighted by diffused lights of unequal intensity. The sphere presents a remarkable example of the manner in which light is distributed over a convex surface, relatively to the eye of an observer, who views it from a given position.

282. I shall not occupy myself with this gradation of white light, from parts illuminated to those which do not appear so. I regard only the principal modifications, and take for examples the cases where they are as evident as possible. These modifications can be reduced to the four following:—

_First modification_, produced by the maximum of white light which the surface of a coloured body is capable of reflecting.

283. Other things being equal, the more highly the surface of a body is polished, the more it will reflect white and coloured light. If we observe the surface of a stick of sealing-wax, suitably placed, we shall perceive a white stripe parallel to the axis of the cylinder, produced by so large a quantity of colourless reflected light that the red light reflected from this stripe is not appreciable by the eye. Thus the white light reflected by a coloured body may be of sufficient intensity to render the colour of the body in some of its parts imperceptible.

_Second modification_, produced by those parts of a coloured surface which send to the eye, in proportion to the coloured light, less white light than the other parts differently lighted, or differently placed in relation to the spectator.

284. When the eye sees certain parts of the surface of a polished or uniformly coloured object which reflects to it proportionally to the coloured light less of white light than the other parts, the first parts will appear in most cases of a more intense tone of colour than the second. We will cite the following:—

_Example 1._—A cylinder of red sealing-wax presents, proceeding from the white stripe mentioned above, a red colour deeper in proportion as less white light reaches the eye. Thus, in a certain position where the white stripe appears to be in the middle of the cylinder, the part most lighted will appear coloured, reflecting a red inclining to scarlet, while that which is the least lighted reflects a red inclining to crimson.

_Example 2._—If the eye is directed into a gold vase of sufficient depth, the gold does not appear yellow as on the exterior surface, but of a red-orange; because less white light, in proportion to coloured light, reaches the eye in the first case than in the second. It is for this reason that the concave parts of gold ornaments appear redder than the convex.

_Example 3._—The spiral thread of a piece of twisted silk or wool held perpendicularly before the eye, appears in the part opposite to the light, of a much more decided colour than on the rest of the surface.

_Example 4._—The folds of bright draperies present the same modification to an eye properly placed; the effect is particularly remarkable in yellow silk stuffs, and in sky-blue; for we can easily understand that it is less marked when the stuffs are less bright and of dark colours.

_Example 5._—There are some stuffs which appear to be of two tones of the same scale of colour, and sometimes also of two tones of two contiguous scales, although the weft and the warp of these stuffs are of the same tone and the same colour. The cause of this appearance is very simple; the threads which, parallel to each other, form the designs, are in a different direction to the threads which constitute the ground of the stuff. Hence, whatever may be the position of the spectator with regard to the stuff, the threads of the design will always reflect coloured and white light in a different proportion to that reflected by the threads of the ground, and, according to the position of a spectator, the design will appear to be lighter or darker than the ground.

_Third modification._—The colour complementary to that of a coloured object developed in one of its parts, in consequence of simultaneous contrast.

285. A natural consequence of the law of simultaneous contrast in general, and of the effect of a colour upon grey and black in particular, is, that since the same object presents some parts more or less dark, contiguous to some parts where we see the colour peculiar to the object, the first parts will appear tinted with the complementary to this colour. But to observe this effect, it is necessary that the grey part should reflect to the eye white light, and little or none of the coloured light which the object naturally reflects.

_Fourth modification_, in a single coloured stuff.

286. For example, if the eye is directed towards a window which admits daylight, and a person clothed in a new blue coat, dyed with indigo or Prussian blue, be at the window, the eye will see one part of the coat will appear different from the other part, because the nap of the cloth is disposed in a contrary direction; one being of a fine blue, while the other is of an orange-grey, by the effect of contrast of the blue part with a part that reflects very little white light to the eye, without, or almost without, blue light.

287. But as the pile of the nap loses its regular position by wear, the cloth becoming dull and soiled, the coloured light is reflected irregularly from all points; and the effect is either absolutely destroyed or much weakened.

If the garment be of a deep green, the grey part will appear reddish; if it be of a violet, maroon, or claret, the grey part will appear yellow.

288. The complementary is only developed upon cloths of dark and sombre colours; thus red, scarlet, orange, yellow, and light blue garments do not exhibit it, because they have always too much of the essential colour which is reflected. The modification occurs only when one of the parts is more strongly illuminated than the other by diffused light (279).

289. There is also one circumstance where the fourth modification will appear evident; it is when we look at a series of light tones—blues, rose, &c. (belonging to the same scale)—of a skein of silk or wool, placed upon an easel, that one-half of the same skein presents to the eye the threads disposed in a contrary direction to those of the other half. The half of the skein which does not reflect coloured light to the eye, appears tinted with the complementary of the other half which does reflect it.

290. Fourth modification in a stuff presenting a dark and a light tone belonging to the same scale.

If we place in juxtaposition a dark tone and a light tone of the same scale, well assorted, the light tone will appear of the colour complementary to the scale to which it belongs. This modification is too important to allow me to pass it over hastily.

291. When we look for several seconds on a fabric dyed with a coloured ground, and on which therefore patterns intended to be white, but which, owing to the imperfection of the process employed, have received a light tone of the colour of the ground, the patterns will appear of the colour complementary to the latter. Thus, upon a ground of yellow-chromate of lead, they will appear violet; upon a ground of orange-chrome, they will appear blue; upon a green ground, rose, &c. To dispel the illusion, and to recognise the true tint of the pattern, it is only necessary to cover the ground with a white paper so perforated as to leave visible only the pattern coloured like the ground. The influence of a dark tone upon a feeble tone is such, that not only is the latter neutralized, but the place it occupies upon the cloth appears also tinted with its complementary colour.

292. From the preceding observations it follows that there may be a printed cotton, the design of which, although coloured, will appear to most eyes white, and not of the complementary of the ground. For those eyes which see it thus, the perception of the phenomenon of contrast will correct the imperfection of the art of the calico-printer.

293. In the Lectures upon Contrast, which I delivered in 1836, at the Gobelins, I remarked, that in applying paper (cut for the purpose) upon the lights of a blue drapery of the Virgin in a tapestry representing the Holy Family, after Raphael, they appeared of a light blue, although, when they were seen surrounded with darker tones, they appeared of an orange tint.

294. We can conceive without difficulty that if the modification is not manifested with monochromous objects of vivid colours, as yellow, scarlet, &c., it is because that part of the surface of these objects which reflects the least light to the eye, always reflects enough of its peculiar colour to neutralize the complementary which the coloured light of the illuminated portion tends to develop. I believe that this effect tends to enfeeble the coloured light of the shaded part.

295. Although, in this chapter, I do not propose to treat of the modifications shown by coloured stuffs with white designs; yet, as it is a case so connected with the preceding considerations, I cannot avoid mentioning them in this place.

296. If we observe a sky-blue silk with white flowers, the weft of which is in an opposite direction to the weft of the blue ground, we shall see the flowers white, if they are placed in the most favourable manner to receive the white light reflected by them; while, in the contrary position, we shall see these flowers absolutely orange. There is still much white light reflected, but it is not sufficiently vivid to neutralize the development of the complementary of the ground.

PAINTING ON THE SYSTEM OF FLAT TINTS.

297. In painting by flat tints, the colours are neither shaded, blended together, nor modified by the coloured rays coming from the surrounding parts of the picture.

In pictures which belong to this kind of painting, the representation of the model is reduced to the observance of linear perspective, to the employment of vivid colours in the nearer parts, and of pale and grey colours in the more distant.

If the choice of contiguous colours has been made conformably to the law of simultaneous contrast, the effect of the colour will be greater than if it had been painted on the system of chiaro-’scuro.

298. In every instance where painting is an accessory, and not a principal feature, painting in flat tints is in every respect preferable to the other kind.

299. The essential qualities of painting in flat tints necessarily reside in the good choice of colours and well drawn outlines. These outlines contribute to render the impressions of colours stronger and more agreeable, when, circumscribing forms clothed in colours, they concur with them in suggesting to the mind a graceful object, when even the imitation of it does not give a faithful representation.

300. We may, in conformity with what has been said, consider that painting in flat tints may be advantageously employed,

1. When the objects represented are at such a distance that the finish of an elaborate picture would disappear.

2. When a picture is an accessory, decorating an object whose use would forbid too elaborate finish, and which would also be too costly. Such are the paintings which ornament screens, work-boxes, tables, &c.; in this case the objects preferable as models, are those whose beauty of colours and simplicity of form are so remarkable as to attract the eye by simplicity of outline, and by vivid colours: such are birds, insects, flowers, &c.